Netgear Nighthawk CAX80 Terrible Up Speeds, lower Down Speeds

I recently swapped my modem/router to the CAX80 model. After the activation my avg. down speeds went from 950-1100Mbps to 700, and my up speed if at a soul-crushing 5Mbps.

The activation service confirmed everything is fine with my equipment, and is sending someone out to see about the Comcast line outside.

However, this makes no sense to me given that it was achieving the prior speeds in the same day with the xfinity modem - which is not as good of a modem!

Some things I've seen online:

1. "You have to wait for the line to warm up" - People have reported speeds picking up over time - perhaps has their system is updated with new info? This seems silly to me, but I've seen it posted here and there.

2. The "provisioning" is wrong (e.g. VoIP included when equipment does not support, etc.).

I have low confidence the tech visit will help (but I am hopeful). Does anyone have any advice or thoughts on this?

Thanks!